The O-Ring (OEM Part No. 0663212901) is a replacement sealing component designed for use in Epiroc / Atlas Copco rock drill assemblies. It is compatible with selected COP rock drill models including COP 1022, COP 1638, COP 1838 and COP 1838HD. The 0663212901 O-Ring helps provide reliable sealing between mating components, maintain fluid and pressure retention and reduce leakage during drilling operation. It is suitable for routine maintenance and replacement when the existing O-ring becomes worn, hardened, damaged or loses sealing performance. The 0663212901 O-Ring helps maintain stable rock drill operation and protect internal components from leakage-related wear.